A clean fuels standard aims to reduce the average carbon intensity of transportation fuels over time. Carbon intensity measures the greenhouse gas emissions that a fuel is responsible for, and it provides a way to compare the efficiency of different transportation fuels. To get a comprehensive picture of carbon intensity, a “well-to-wheels” analysis is used.
Well-to-Wheels is a comprehensive approach
A well-to-wheels approach looks beyond the emissions produced during vehicle operation, or tailpipe emissions, and considers the emissions associated with producing and transporting fuels. This methodology provides a holistic approach to measuring emissions by examining the entire energy consumption and greenhouse gas emissions produced as a result of fuel production, processing, distribution, and operation. It looks at the direct and indirect effects of the entire lifecycle of the fuel source.
The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model is a transparent platform that the US Department of Energy recommends for evaluating the energy and environmental effects of vehicle technologies and fuels. The GREET model uses a well-to-wheels emissions analysis to simulate the energy use and emissions outputs of vehicle and fuel combinations and calculate a credible carbon intensity score.
It’s important to note that the well-to-wheels analysis is fuel and technology-specific. For example, renewable natural gas can be produced by capturing methane emitted from the breakdown of organic waste that would otherwise have escaped into the environment. Although there are some emissions released from the combustion of renewable natural gas, the emissions savings from capturing the gas can outweigh those produced by its use, resulting in a negative carbon intensity score.
When it comes to electric vehicles, it’s essential to consider not only the emissions from the vehicle while in use but also the carbon emissions required in the generation of electricity. Electricity generated from renewable sources will have a lower carbon intensity than electricity generated from coal or natural gas.
Why is this important for a Clean Fuels Standard?
Using a well-to-wheels approach to measure carbon intensity ensures that there is a credible assessment of emissions, making sure that the clean fuel standard will be effective in reducing emissions economy-wide. With credible and comprehensive carbon intensity scores, a clean fuel standard is the right policy to reduce carbon emissions from all transportation fuels and help reduce total global emissions.
